Quattro bar: public per-screen visibility override API for plugins

[SamCod3]

Motivation

Quattro supports service and bar-widget plugins, but the stock bar currently
owns visibility through the single global bar-off state. A plugin that wants
to implement policies such as per-workspace visibility, presentation mode or
custom autohide has no supported way to ask the stock bar to hide one screen.

Today such a plugin must either mutate internal properties such as barHidden
or PanelWindow.visible, or continually translate its policy into the global
bar-off flag. Both approaches couple the plugin to implementation details and
become fragile across startup, output reconstruction and suspend/resume.

Suggested extension point

Could the stock bar expose a small, documented, per-screen visibility override
API for service plugins? The exact names are not important, but conceptually:

setScreenHiddenOverride(ownerId, screenName, hidden)
clearScreenHiddenOverrides(ownerId)

This could live directly on the public bar interface or behind a stable shell
wrapper that forwards to the active bar.

Suggested semantics:

• Requests are idempotent and keyed by plugin owner plus screen/output.
• hidden: true adds that owner's hide request; hidden: false removes it.
• The existing global bar-off state remains authoritative and unchanged.
• A panel is effectively hidden when global bar-off is set or any owner has a
  hide request for that screen.
• Bar.qml remains the sole owner of margins, exclusion mode, parking and the
  PanelWindow lifecycle.
• Newly created or remapped BarPanel instances automatically inherit the
  current effective state through a normal binding.
• Overrides are removed when their owning plugin is unloaded or disabled.

The policy and any persistence would remain the responsibility of the plugin.
For example, a plugin could observe the workspace displayed on each monitor,
persist its own workspace -> hidden map, and update this API without touching
bar internals or the global marker.

Why per-screen rather than global

The stock bar already creates one BarPanel per screen. A global API would not
support multi-monitor policies: two screens can simultaneously display
workspaces whose desired states differ. Passing the output name keeps the API
narrow without exposing BarPanel objects to plugins.

Compatibility

• No behavior changes unless a plugin uses the API.
• bar-off and omarchy-toggle-bar retain their current global behavior.
• Existing bar widgets remain unchanged.
• Plugins do not receive access to the underlying window, margins or exclusion
  properties.

Minimal acceptance cases

1. Hiding one output does not affect another output.
2. The hidden output has no exclusion zone and uses the stock parking behavior.
3. Clearing the request restores the global bar state.
4. Global bar-off still hides every bar regardless of plugin requests.
5. Recreating an output or BarPanel preserves the effective override.
6. Disabling the owner plugin removes all of its overrides.

This would provide a general extension point rather than implementing any one
policy in Omarchy itself.

[RodriMora]

This API would enable a useful laptop + external monitor workflow: autohide the bar only on the integrated laptop display while leaving it permanently visible on the external monitor.

My setup is Omarchy 4.0.0-1 with two Hyprland outputs:

• eDP-1: integrated laptop display — desired behavior is autohide, revealing the bar when the pointer touches the top edge
• DP-1: external display — keep the top bar always visible

The current global bar-off state cannot express this because it hides both bar surfaces. A per-screen visibility override like the one proposed here would let an autohide policy/plugin implement this without cloning or depending on Bar.qml internals.

Helps with OLED screens burn in too